The present invention relates generally to the field of disc drive data storage devices, and more particularly but not by way of limitation, to crash stops for limiting the movement of an actuator of the disc drive and the installation of various components onto a basedeck to provide flushing engagement thereon.
Modern disc drives are commonly used in a multitude of computer environments, ranging from super computers to notebook computers, to store large amounts of data in a form that is readily available to an end user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc has a data storage surface divided into a series of generally concentric data tracks radially spaced across a band having an inner diameter and an outer diameter. The data is stored within the data tracks on the disc surfaces in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors where data is stored in fixed size data blocks.
The read/write head includes an interactive element such as a magnetic transducer. The interactive element senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the interactive element transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
Each of the read/write heads is mounted to a rotary actuator arm and is selectively positioned by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the track. The read/write head includes a slider assembly having an air bearing surface that, in response to air currents caused by rotation of the disc, causes the head to fly adjacent to the disc surface with a desired gap separating the read/write head and the corresponding disc.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively, the discs, spacer rings and spindle motor hub define a disc pack assembly. The surfaces of the stacked discs are accessed by an actuator assembly which includes the read/write heads and the complementary stack of actuator arms. The actuator assembly also includes head wires which conduct electrical signals from the read/write heads to a flex circuit connector mounted to a disc drive base deck.
When the disc drive is not in use, the read/write heads are brought to rest in a landing zone which is separate from the data storage locations of the discs. The landing zone provides a non-data storage location on each of the disc surfaces where the read/write heads are positioned before the rotational velocity of the spinning discs decrease below a threshold velocity which sustains the air bearing. The landing zone is typically located near the inner diameter of the discs.
A continuing trend in the industry is the simultaneous reduction in size and increase in data storage capacity and processing speed of modern disc drives. As a result, the discs of modern drives increasingly have smaller diameters and tighter disc-to-disc spacings. Although providing increasing amounts of storage capacity, narrow vertical spacing of the discs gives rise to a problem of increased sensitivity to operational vibrations and to external mechanical shock. Additionally, as disc drives continue to decrease in size, smaller heads, thinner gimbal assemblies continue to be incorporated into these drives. Faster seek times also demand increased velocity of the actuator assembly. These factors significantly increase the need to protect the disc drives from incidental contact between the actuator arm/gimbal assemblies and the disc surface.
The requirement for these non-data storage locations on the disc works counter to the general trend for ever increasing data storage capacity. As a result, it is necessary to limit the size of the non-data zones, and to precisely control the extent of actuator travel relative to the non-data zones. Otherwise, an actuator that travels beyond the desired extent of radial travel likely results in damage to the read/write head. The inner extent of radial travel allows the read/write head to travel inwardly past the inner most data track to the landing zone where the read/write head can be parked on the disc surface when the disc drive is non-operational. Inward travel beyond this inner extent can result in damaging contact of the read/write head with the spindle motor hub. The outer extent of radial travel allows the read/write head to access the outermost data track. Outward travel beyond this outer extent of travel can result in the read/write head moving beyond the outer edge of the data disc where there is no sustaining airflow, causing damage to the read/write heads which can contact one another or the spinning discs.
As requirements for faster data processing demand ever increasing actuator speed and associated deceleration rates during seek cycles, the likelihood of overshooting the target track increases. Such an overshoot near the extents of travel can result in damage to the read/write heads. Also, unfortunately, control circuit errors are known to create xe2x80x9crunawayxe2x80x9d conditions of the actuator wherein the actuator fails to decelerate at the appointed time. To protect the read/write heads from catastrophic failure, it is well known and practiced in the art to employ positive stops that limit the actuator travel to locations only between the desired extents of travel.
In providing such a positive stop, or end stop, it is necessary that the end stop decelerate the actuator quickly and in a short distance, but without damaging the actuator assembly. The maximum deceleration is limited to that which is below the acceleration force limits of the actuator assembly, such as below the deceleration force that would cause the transducer to deflect away from a supporting member and thereby either contact the data storage surface or deform the end stop. As a result, numerous attempts to provide a controlled braking impulse to the actuator have been made.
Applying a general dampened braking impulse is known in the art, such as by the use of an air cylinder type dampener as taught by U.S. Pat. No. 4,937,692 issued to Okutsu. In this approach, fluid is displaced by a piston that is responsive to a stop member that obstructs the movement of the actuator beyond the desired extent of travel. The dampened braking impulse provides a resistive force for decelerating the actuator, but without the typical sudden deceleration of a rigid stop member, such as a rigid stop pin.
Manufacturability and cost constraints have urged the art toward more simple mechanisms. The use of a resilient pad is widely known, such as that of the teaching of U.S. Pat. No. 4,890,176 issued to Casey et al. and assigned to the assignee of the present invention. Spring members, too, are widely used in the art, such as that according to the teachings of U.S. Pat. No. 4,635,141 issued to Hazebrouck.
The primary objection to resilient pads and springs is the relatively long stopping distance necessary to compress the response member sufficiently so as to develop an effective braking force. One attempted solution is to provide cantilevered members that elastically deflect in response to the impact force of the actuator, such as is taught by U.S. Pat. No. 5,134,608 issued to Strickler et al. and U.S. Pat. No. 5,600,516 issued to Phillips et al. and assigned to assignee of the present invention.
Another objection to resilient pads or other fixed objects is the inherent problems relating to the loading and unloading of the read/write heads on to and off of the discs. If the end stop is fixedly mounted to limit the movement of the actuator arm, the end stop must be installed after the heads have been loaded (merged) onto the discs. Furthermore, in order to unload the heads (de-merge), the outer stop must then be physically removed. It is well known in the art to provide an end stop capable of being manually displaced from the rotational path of the actuator to allow the loading of the heads on the disc, as taught by U.S. Pat. No. 5,134,608 issued to Strickler et al.
The end stop must be capable of providing an effective deceleration for an actuator, limiting the movement of the head in such a manner to prevent any deleterious effects. Furthermore, the end stop must be capable of allowing for the merge and de-merge of the heads.
Another problem often encountered with disc drives is during the assembly process and is the orientation of the various components as they are installed onto the basedeck. Furthermore, the order in which components may be installed in the drive directly affects the speed of assembly. Often times, various components cannot be installed until other components are initially secured within the drive or to the basedeck. A common problem occurs during the installation of the actuator assembly and the outer stop onto the basedeck. As the outer stop prohibits movement beyond the outer extent, the actuator assembly must be installed first and then the outer stop attached, often times requiring additional installation steps, slowing down the assembly process.
A continuing trend in the industry is the development of an assembly method commonly referred to as xe2x80x9ctop down assemblyxe2x80x9d where the installation begins with the basedeck and the components are continuously inserted thereon in a prescribed order. When the outer stop must be installed after the installation of the actuator assembly, this provides for an inefficient assembly process. Furthermore, there is a trend in the industry to reduce the number of individual components assembled into the drive. One particular solution is the pre-installation of components onto other components prior to their installation within the basedeck assembly.
Another problem associated with the assembly of multiple components in a disc drive is the spatial relationship between the various components. Many of these components synchronously work together to provide the capabilities of the drive and they must be positioned relative to each other within specific tolerance ranges. It is well known to orient multiple components relative to a fixed reference, such as the basedeck.
Another problem commonly found during disc drive assembly is the installation of the various components and their flushing engagement with other components, such as with the basedeck. To compensate for manufacturing tolerances, boss members may be installed on the basedeck for providing engagement with the various components. A problem exists in that when the components are secured to the basedeck, it may cause the mechanical component to displace from flushing engagement with the boss member and may produce a bowing effect within the component itself.
As such, within the industry there currently exists a need in the art for an end stop capable of allowing the merging and de-merging of the heads of the actuator while the outer stop is maintained in a fixed position and providing a proper limiting force for the actuator itself. There also exists a need in the industry to provide an outer stop that allows the installation of the actuator assembly after the outer stop has been installed. Furthermore, there is a need in the art to provide for easier assembly of a disc drive through the installation of fewer individual components and providing for these fewer components to be referenced relative to common reference points. Finally, there exists a continuing need for the improved installation of the various components within the drive, consonant with the top-down assembly and providing for the components to be flushingly engaged with the basedeck.
The present invention provides a moveable outer stop for a disc drive assembly, wherein the disc drive assembly has a disc pack with a data storage disc having a landing zone and a data storage zone thereon. The disc pack includes a spindle motor for rotating the disc. An actuator in the disc drive assembly is rotatably supported in a plane parallel to that of the disc and supports an array of read/write heads in a radial movement across the disc in data reading and writing relationship to the disc.
The disc drive has a voice coil motor that operably moves the actuator to move the read/write heads radially between the parked location and the data storage location. The parked location provides a landing zone for the read/write heads when the drive is non-operational. The voice coil motor includes a magnet assembly having a pair of opposing magnet members supported by a pair of opposing poles. In moving the actuator it is advantageous to constrain movement of the read/write heads to positions within an inner and an outer extent of travel, which includes the data storage locations and the landing zone. In preventing movement of the read/write heads beyond the outer extent, an end stop, or outer stop, is provided.
The outer stop comprises a base plate fixedly positioned within the basedeck, attached to the pole piece with a post extending upward therefrom. A cantilevered arm extends outward from the post, the arm comprising a proximal end connecting the arm to the post and a distal end for contact engagement with the actuator. The distal end is capable receiving a displacement force from the actuator as the heads are merged onto the discs and also receiving a compression force from the actuator when the heads are rotated past the outer extent of the disc. The cantilevered arm is displaceable in a rotational direction substantially about the post and deformable in a direction substantially along the its longitudinal axis. Furthermore, the arm is composed of a compressible curved beam, deformable in response to the compression force.
The arm is also rotationally displaceable in response to a displacement force applied to the distal end of the arm, causing the arm to be rotationally displaced about the post, allowing the actuator full rotation without contacting engagement with the distal end of the arm. Thereby, when the heads are merged or de-merged, the end stop of the present invention may be effectively displaced while the actuator passes the outer extent, and the arm is then biased back to its original position upon cessation of the displacement force.
Furthermore, when the actuator rotates into contacting engagement with the outer stop while the heads are over the discs, the arm limits the movement of the actuator through its deformability along its longitudinal axis and when the actuator rotates into contact engagement with outer stop prior to the heads being merged, the actuator exerts a displacement force, displacing the arm and allowing the actuator assembly to freely rotate, positioning the heads over the discs. Whereupon, a biasing force returns the end stop to its limiting position once the heads are merged.
Another aspect of the present invention is that the end stop is fixedly attached to a pole piece adjacent the voice coil magnet. During the top-down assembly process, the pole piece is positioned onto the basedeck of the drive, with the end stop already attached thereon. On the posterior side of the end stop, to facilitate flushing attachment to the pole piece and the pole piece to the basedeck, are disposed multiple engagement features. A first engagement feature engages a first receiving member in the pole piece, whereas a second engagement feature is disposed in a second receiving member having an aperture disposed therein. The second engagement feature not only engages the second receiving member, but also extends through the aperture for contacting engagement with a boss element on the basedeck.
The pole also provides a third engagement feature disposed on its posterior side. This engagement feature may be provided by a latch mechanism attached to the pole piece having an engagement feature extending therethrough, or the pole piece may be designed to have an engagement feature already disposed thereon. Irrespective, the pole piece itself has at least two engagement features projecting from its posterior side. During installation, the engagement features of the pole piece are placed on boss members projecting upward from the basedeck.
After the pole piece has been properly mounted, fasteners are inserted through the pole piece into the basedeck. The receiving voids for receiving the fasteners are strategically disposed in close proximity to the boss members whereby the insertion of specific fasteners provide the pole piece flushing engagement with the basedeck.
Wherein, the actuator assembly may then be installed into the drive upon a cartridge bearing assembly extending from the basedeck. The outer stop may then be subjected to a displacement force created by the actuator contacting the distal end of the arm, displacing the arm and allowing the actuator assembly to rotate about the cartridge bearing assembly, merging the heads onto the disc surface.
These and other advantages and features of the present invention will be apparent from the following description when read in conjunction with the drawings and appended claims.